1. Field
The present invention relates to medical technologies, and particularly, to a pacemaker signal detecting method, a pacemaker signal detecting system, and an electrocardial detecting device.
2. Background
Bradycardia means low cardiac frequency, probably accompanied by rhythm disturbance. The cardiac frequency of the bradycardia is normally lower than sixty beats per minute. A heart of a patient suffering from serious bradycardia cannot provide enough oxygen-rich blood to the body. As a result, the patient shows symptoms of dizziness, hyposthenia, shortness of breath, and even syncope, which adversely affects living quality of the patient and may endanger the life of the patient. Pacemaker implantation is a common therapeutic solution to the bradycardia. A pacemaker transmits a small electric signal to the heart to increase the cardiac frequency, helping the heart to recover to a normal rhythm and relieve the symptoms of bradycardia. Electrocardial detecting devices or electrocardial diagnostic devices, such as an electrocardiograph, provide a non-invasive and quick way to detect a pacemaker signal, and they may also be used in patient monitoring and other aspects, such as patient recognizing and diagnosing after the pacemaker is implanted.
A detecting range of the pacemaker signal is specified in an electrocardial monitoring standard and an electrocardiograph standard, wherein the detecting range of the pacemaker signal to a patient monitor is 0.1 millisecond (ms) to 0.2 ms in width and ±2 millivolt (my) to ±700 my in amplitude. However, because the pacemaker is an implanted device, power supply is a main problem needed to be solved by the pacemaker. In order to increase service life of a battery of the pacemaker, pacemaker manufacturers need to reduce the power consumption of the pacemaker and improve efficiency of the pacemaker. Such improvements may increase the service life of the battery, but effectively lead to smaller amplitudes of the pacemaker signal when measured at the body surface and difficulty in detecting the pacemaker signal.
Furthermore, due to projection relationships between the pacemaker signal and different electrocardial lead axis, the amplitude of the pacemaker signal in the different electrocardial lead axis show great differences thereamong when the pacemaker signal is conducted to, and measured at, the body surface. With development of the pacemaker technology, a pacemaker which meets related standards cannot completely meet demands of clinical use. American Electrocardiology Society also advises that monitoring device manufacturers should improve detection of the pacemaker signal. Currently, most of the monitoring device manufacturers apply a hardware method to detect the pacemaker signal. A basic principle of the hardware method is to detect slew rate and amplitude of the pacemaker signal. However, since a strategy of detection by hardware is very simplistic, the shapes of the pacemaker signals cannot be detected and the hardware method also fails to adaptively adjust detection threshold based on changes of the pacemaker signal and ambient noise. Thus, the hardware method is very vulnerable to interference. Some manufacturers compromise the threshold detection values to improve the immunity of the interference on a pacemaker signal detecting module, but that lowers the sensitivity of detection.